Quantitative Trait Loci for Antixenosis Resistance to Corn Earworm in Soybean
1999
Rector, B. G. | All, J. N. | Parrott, W. A. | Boerma, H. R.
Insect resistance in soybean, Glycine max (L.) Merr., is inherited quantitatively and has been difficult to incorporate into high-yielding cultivars. The objectives of this study were to: (i) use restriction fragment length polymorphism (RFLP) markers to identify quantitative trait loci (QTLs) for antixenosis (nonpreference) resistance to corn earworm, Helicoverpa zea Boddie, in soybean plant introductions PI171451 and PI227687, (ii) determine the location of the QTLs on the public soybean genetic linkage map, (iii) determine their relative magnitude and gene action, and (iv) compare them to insect resistance QTLs previously detected in PI229358. RFLP maps were constructed in two insect-susceptible × insect resistant soybean populations: Cobb × PI171451 and Cobb × P1227687. Insect resistance was measured either in the field or greenhouse as percentage defoliation by corn earworm on vegetative soybean plants. Marker-QTL associations were detected by interval mapping and confirmed by single-factor analysis of variance. Comparisons were made between QTLs identified in this study and those identified previously using PI229358 as the source of insect-resistant germplasm. Among the three resistant genotypes (PI171451, PI227687, and PI229358) a QTL on linkage group (LG) ‘H’ was shared among all three genotypes (accounting for an R₂ of 19,9, and 17%, respectively), and a major QTL on LG ‘M’ was shared between PI171451 and PI229358 (R₂= 37% for each). A minor QTL on LG ‘C2’ was identified which was unique to PI227687 (R₂= 11%) and a minor QTL on LG ‘D1’ was identified which was unique to PI229358 (R₂ = 12%). In addition, a QTL was found on LG ‘F’ in the susceptible genotype, Cobb (R₂ = 20%). This QTL is in a region of the soybean genome which has been previously associated with a cluster of soybean pathogen-resistance loci.
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